In an internal combustion engine of the piston and cylinder type, nearly all designs in use in automotives today utilize “poppet” valves which intermittently open to allow intake of air and exhaust of waste gases, and close to permit the cylinders to carry out the compression and combustion cycles of the engine. A conventional poppet valve typically is spring loaded and works in conjunction with rocker arms, lifters and a camshaft the timing of which is linked ultimately to the engine crankshaft. Ideally the cycles of valve opening and closure taking place within this high pressure and high temperature environment are unimpeded by friction or parts failure, and closure is sufficiently secure to maximize compression, fuel burning and engine performance.
However, the operation of a conventional poppet valve depends upon the interaction of numerous small parts, is subjected to excessive wear, and suffers various inefficiencies. These inefficiencies include, for example, parasitic loss in the form of friction and reciprocating inertia, and pre-ignition due to high exhaust valve temperatures. These various inefficiencies often result in excessive emissions, excessive fuel consumption, and vibration and noise including, for example “engine knocking”. In addition, the performance of each poppet valve and associated components also depend upon a significant volume of oil and the accompanying need for frequent oil change.
A significant source of parasitic loss in a poppet valve system is the inertial loss from reciprocating components. Moreover, as there are two or more poppet valves in use per cylinder, there are many valves total in operation for each automotive engine. The valve bodies, lifters, pushrods, and springs in operation for each valve all have a mass that is twice accelerated and decelerated every other crankshaft revolution. These loads are continually taking power from the engine, and increase exponentially with increase in engine speed.
Rotary valves offer several advantages over poppet valves. For example, at constant engine speed, a rotating cylindrical valve assembly bears no inertial load on an engine. Inertial loads with a rotary valve are born by the engine only during acceleration and deceleration and are typically extremely low. In addition, rotary valves improve the coefficient of gas flow as compared to similar sized poppet orifices and allow much larger peak valve areas than poppet valves, thereby improving high speed operation. The use of rotary valves such as those disclosed herein requires only one port in the roof of the combustion chamber to serve as both the intake and exhaust valve, thereby allowing the entire valve area to be dedicated to both intake and exhaust as required. Further, this port is unobstructed unlike with a poppet valve, the body of which obstructs a port to reduce flow in both intake and exhaust. Air flow is thereby significantly higher with the invention disclosed herein, enabling higher volumetric efficiency at high engine RPMs. Increased flow at higher RPMs increases an engine's peak power potential and therefore can enable the use of smaller more fuel efficient engines where a larger engine would otherwise be required. Engine speed moreover is not limited by a rotary valve as they are by a poppet valve. And finally, rotary valves have a much larger thermal mass and heat transfer area than a poppet valve or valves, thereby significantly reducing in-cylinder peak component temperatures to greatly lower the likelihood of pre-ignition (knocking). A lower valve temperature also allows greater compression ratios to significantly improve engine thermal efficiency.
With a world oil market price surpassing seventy dollars a barrel and predictions of ever increasing global demand and price, the high cost of dependence upon foreign sources of oil, and dire warnings from climatologists about the impending irreversible global change resulting from greenhouse gases, there is a need for innovation of the internal combustion engine to reduce its consumption of oil and its emissions, and to improve its overall efficiency. Increased fuel efficiency and reduced oil consumption and emissions and smoother operation are among the potential advantages of a rotary valve.
Numerous rotary valve designs have been proposed to replace the more conventional poppet valve. However, various drawbacks of previous designs have rendered such designs thus far incapable of achieving these objectives. For example, the continued need for lubricating oil for operation of the rotating valve assembly, and the consequential increased emissions from the burning of oil as the oiled valve assembly surface rotates into the combustion chamber are characteristic drawbacks. Achieving adequate combustion chamber sealing is a continuing challenge of a successful rotary valve system, especially under the substantial pressures and thermal stresses of an internal combustion engine and the rotational forces of a rotary valve. These challenges have led to a need in the art for a rotary valve assembly that does not suffer these drawbacks. Further, there is a need in the art for a valve designed to vary the valve parameters of timing, duration, and valve area, based upon the instantaneous demands on the engine.